C4 Rack-And-Pinion Rebuild - A Turn for the Better

Rebuilding the C4 rack-and-pinion for trouble-free performance on the street or track

Generally speaking, the rack-and-pinion steering systems of C4 Corvettes are dependable performers, and most enthusiasts don't give them a second thought unless they go bad. For the average street car, that doesn't happen, but if your C4 sees a lot of duty in track-day events or is a more dedicated race car, there are some vulnerabilities. For one thing, the power-steering fluid can overheat and damage—or kill—the pump. The rack-and-pinion unit is susceptible to damage from leaking seals and torn boots, conditions brought on by dirt and debris. Left unchecked, these leaks allow the pump to run out of fluid, possibly burning it up and damaging the rack.

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Taking care of the power-steering pump is a pretty easy fix—it's simply replaced with a new one. There's no such remedy for the rack-and-pinion unit, however, because it's no longer manufactured. Options, then, are limited to scouring Craigslist and salvage yards for a used part or having the original unit rebuilt. Only a few companies around the country perform the procedure, and we recently stopped by Saginaw, Michigan's Turn One to see how it was done.

It's no coincidence that Turn One is located in Saginaw, because founder Jeff Roethlisberger spent 14 years at the well-known Saginaw Steering plant as a ride-and-handling engineer, specializing in steering development. His shop is located only about 4 miles down the road from the factory, which has undergone a number of ownership changes in recent years (see sidebar). He started the company in 1997, specializing in motorsports steering systems.

Rebuilding the C4 Corvette racks was a part of the business that was born out of necessity, because as we mentioned earlier, new racks are no longer available.

"Fortunately, most of the rack-and-pinions we receive are suitable for rebuilding," says Roethlisberger. "The only thing that keeps us from rebuilding one is if the rack itself is severely damaged or bent."

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After receiving the rack-and-pinion unit, typically with the inner tie rods still attached, Turn One completely disassembles it. The components are cleaned and inspected, and the seals replaced. New boots are installed, if necessary, and the entire system is carefully reassembled. As is often the case with such projects, the process is pretty straightforward, but not exactly simple. For example, extreme care must be taken to line up the pinion precisely on the rack during reassembly, to ensure the steering wheel will be straight in the car. Turn One even mounts the rebuilt rack-and-pinion on a specialized dynamometer to check its performance.

Considering the fact that new C4 rack-and-pinion units are no longer available, and the rebuilding process is so specialized, we were pleasantly surprised by Turn One's approximate $200 charge for the service. With the costs of other chassis- and suspension-related components easily costing two or three times that, a fresh rack-and-pinion setup seems well worth the money. A turnaround time of about two weeks is standard, with the customer supplying the core for rebuilding. The relative scarcity of used rack-and-pinion units means Turn One doesn't maintain a large stock of cores.

We followed along as Turn One's Bill Meschke performed a standard rebuild. For the sake of our photos, he focused on a unit that had already been cleaned up, which provided better views of the disassembly process. The accompanying shots and captions depict the significant steps in the procedure.
If your C4 isn't carving the turns like it used to, a rack-and-pinion rebuild may be just the thing to steer it straight again.

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C4 Rack-And-Pinion Rebuild - A Turn for the Better

Here’s the rebuilt and refurbished C4 rack-and-pinion assembly, ready to provide years more service on the street or track. Considering C4 rack-and-pinion units are no longer manufactured, Turn One’s service is downright cheap at about $200.

After receiving a steering-rack assembly, Turn One begins the refurbishment by completely disassembling it, starting with the removal of the tie-rod boots. A couple of clamps hold them in place, but the job gets messy quickly if the rack’s seals were breached and fluid leaked into the boots.

With the boots out, the tie rods themselves are removed next. It’s a relatively simple process to loosen them, but it requires a healthy dose of leverage. With one end of the assembly held in a vice, a long lever is used over a wrench to break free the fastener.

After the tie rods are removed, the steering-rack shaft itself is exposed. It protrudes from both sides of the rack housing, and careful measurements must be taken to ensure it is centered in the housing. The center point determines the position of the “whistle notch.”

The whistle notch is seen here as the divot on the shaft (left side of photo). Its position, as determined and described in the previous caption, must be matched exactly during reassembly or the car’s steering wheel won’t be straight.

Next, the position of a pinion pre-load adjuster is noted to determine if it’s out of alignment, and, if so, how badly. The adjuster sets the pre-load of the pinion teeth into the rack teeth. It has to be just right to ensure normal steering effort and prevent unnecessary wear.

After the adjuster position is recorded, it is removed, revealing the adjuster spring and, beneath it, a steering-rack bushing. In almost all cases, the spring and rack bearing are reused.

With the adjuster spring and rack bearing removed, the valve that incorporates the pinion is pulled out. Generally, the pinion itself is almost always in fine condition, but the Teflon rings on the valve may require replacement.

The removal of the valve/pinion pretty much completes the disassembly of the rack. All the pieces are moved to a parts washer, where they’re thoroughly degreased, cleaned, and inspected.

Next, the rack housing and shaft take a quick spin in a lathe to check for any obvious signs they aren’t straight. That’s generally a problem only if the vehicle the rack came from was in an accident. For the most part, this process simply confirms that the housing and/or shaft are good to reuse, because a bent housing or shaft isn’t really repairable—and the next step would be jumping on eBay to look for a used rack.

The reassembly stage commences with the pressing of the pinion bearing into the housing. Like many of the other components, the original pinion bearing is a robust piece that simply requires cleaning and repacking in order to reuse it.

The rack shaft is shown here being inserted in the rack housing, wearing a generous dollop of chassis grease on the teeth, as well as on the backside of the shaft. That’s because the bearing rides all around the shaft

Here, the rack seal is seated into the housing. New seals are used, as they are generally the failure points that bring racks to Turn One in the first place.

The next steps involve installing inner and outer bulkheads over the rack shaft. Here, the inner bulkhead is pushed into place. A bushing is used with it to keep the rack centered.

After the inner bulkhead comes the outer bulkhead, which is installed with a new O-ring and an additional seal. With the bulkheads in place, the rack is ready to be married with the pinion.

Before the pinion/valve assembly is installed, it’s prepared with the same chassis grease as the rack shaft. The Teflon seals on the valve are new, too, on this part.

The rack shaft’s center point is reset to the measurements taken during disassembly, so that when the pinion is installed, the whistle notch will be in that all-important original position.

Here, the valve/pinion is pushed into place, meshing it with the rack teeth. To ensure the whistle notch is in the correct position, the pinion must not be off by even a single tooth on the rack. If it is, the valve is pulled out and carefully reinstalled—a process repeated until the alignment is perfect.

With the pinion correctly positioned, the rack bushing and adjuster spring are greased and lubed, respectively, and reinstalled.

The adjuster is reinstalled, and the preload is set. That’s done by tightening it to 10 Newton meters and backing it off 60 degrees. After that, the fastener is tightened to hold the adjuster in place.

Reassembly wraps up with the installation of the cleaned-and- inspected hydraulic lines. Again, an accident may damage them, but unlike the housing and rack shaft, that doesn’t necessarily mean “game over.” Turn One has the capability of having new lines constructed.

The fully assembled rack-and- pinion unit is put on Turn One’s unique test dyno, which is used to perform a series of functionality inspections. These include basic leak checks at the seals, a pressurized test for internal leaks, and a “pressure effort” test on the valve, which involves “turning” the rack back and forth. In all, each rack spends about 20 minutes on the dyno.

After successfully passing all the tests and inspections on the dyno, the tie rods are reattached to the rack and new boots are installed.

Here’s the rebuilt and refurbished C4 rack-and-pinion assembly, ready to provide years more service on the street or track. Considering C4 rack-and-pinion units are no longer manufactured, Turn One’s service is downright cheap at about $200.

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